Q&A（FAQ）
Where is noise sources and pathway in PSU?

1. Souces

Some noise will occur from the switching power supply because it operates by controlling the switching high voltage. Their main sources are shown in Fig.2.1

  1. Switching transistor ----- (a)
  2. Output rectifier ----- (b)
  3. Output transformer ----- (c)

2. Pathways

The noises occurring from power supply are classified into several kinds as shown below based on the pathways. The pathways of noise are shown in Fig.2.1

  1. Line conduction: Conducted from input terminal of power supply
    • Differential-mode noise: Occurring between the AC input lines ----- j
    • Common-mode noise: Occurring between the AC input line and FG ----- k
  2. Output noise: Conducted from output terminals of power supply
    • Differential-mode noise: Occurring between output lines ----- l
    • Common-mode noise: Occurring between the output line and FG ----- m
  3. Radiated emission: Radiating from power supply or input/output line directly ----- n
    (Radiation noise)

Fig.2.1 The souces and pathways of noise

Technical Product-related Inquires

e-mail:support@cosel.co.jp